Publications

The synthesis of low-cost and highly active electrodes for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is very important for water splitting. In this work the novel amorphous iron-nickel phosphide (FeP-Ni) nanocone arrays as efficient bifunctional electrodes for overall water splitting have been in-situ assembled on conductive three-dimensional (3D) Ni foam via a facile and mild liquid deposition process. It is found that the FeP-Ni electrode demonstrates highly efficient electrocatalytic performance toward overall water splitting. In 1 M KOH electrolyte the optimal FeP-Ni electrode drives a current density of 10 mA/cm2 at an overpotential of 218 mV for the OER and 120 mV for the HER and can attain such current density for 25 h without performance regression. Moreover a two-electrode electrolyzer comprising the FeP-Ni electrodes can afford 10 mA/cm2 electrolysis current at a low cell voltage of 1.62 V and maintain long-term stability as well as superior to that of the coupled RuO2/NF‖Pt/C/NF cell. Detailed characterizations confirm that the excellent electrocatalytic performances for water splitting are attributed to the unique 3D morphology of nanocone arrays which could expose more surface active sites facilitate electrolyte diffusion benefit charge transfer and also favorable bubble detachment behavior. Our work presents a facile and cost-effective pathway to design and develop active self-supported electrodes with novel 3D morphology for water electrolysis.

In this work CdS/SiC/TiO₂ tri-composite photocatalysts that exploit electron- and hole-transfer processes were fabricated using an easy two-step method in the liquid phase. The photocatalyst with a 1:1:1 M ratio of CdS/SiC/TiO₂ exhibited a rate of hydrogen evolution from an aqueous solution of sodium sulfite and sodium sulfide under visible light of 137 μmol h⁻¹ g⁻¹ which is 9.5 times that of pure CdS. β-SiC can act as a sink for the photogenerated holes because the valence band level of β-SiC is higher than the corresponding bands in CdS and TiO2. In addition the level of the conduction band of TiO2 is lower than those of CdS and β-SiC so TiO₂ can act as the acceptor of the photogenerated electrons. Our results demonstrate that hole transfer and absorption in the visible light region lead to an effective hydrogen-production scheme.

A technoeconomic analysis of photoelectrochemical (PEC) and photovoltaic-electrolytic (PV-E) solar-hydrogen production of 10 000 kg H₂ day⁻¹ (3.65 kilotons per year) was performed to assess the economics of each technology and to provide a basis for comparison between these technologies as well as within the broader energy landscape. Two PEC systems differentiated primarily by the extent of solar concentration (unconcentrated and 10× concentrated) and two PV-E systems differentiated by the degree of grid connectivity (unconnected and grid supplemented) were analyzed. In each case a base-case system that used established designs and materials was compared to prospective systems that might be envisioned and developed in the future with the goal of achieving substantially lower overall system costs. With identical overall plant efficiencies of 9.8% the unconcentrated PEC and non-grid connected PV-E system base-case capital expenses for the rated capacity of 3.65 kilotons H₂ per year were $205 MM ($293 per m² of solar collection area (m_S⁻²) $14.7 W_H2P⁻¹) and $260 MM ($371 mS−2 $18.8 W_H2P⁻¹) respectively. The untaxed plant-gate levelized costs for the hydrogen product (LCH) were $11.4 kg⁻¹ and $12.1 kg⁻¹ for the base-case PEC and PV-E systems respectively. The 10× concentrated PEC base-case system capital cost was $160 MM ($428 m_S−2 $11.5 WH₂P⁻¹) and for an efficiency of 20% the LCH was $9.2 kg−1. Likewise the grid supplemented base-case PV-E system capital cost was $66 MM ($441 _mS⁻² $11.5 W_H2P⁻¹) and with solar-to-hydrogen and grid electrolysis system efficiencies of 9.8% and 61% respectively the LCH was $6.1 kg⁻¹. As a benchmark a proton-exchange membrane (PEM) based grid-connected electrolysis system was analyzed. Assuming a system efficiency of 61% and a grid electricity cost of $0.07 kWh⁻¹ the LCH was $5.5 kg⁻¹. A sensitivity analysis indicated that relative to the base-case increases in the system efficiency could effect the greatest cost reductions for all systems due to the areal dependencies of many of the components. The balance-of-systems (BoS) costs were the largest factor in differentiating the PEC and PV-E systems. No single or combination of technical advancements based on currently demonstrated technology can provide sufficient cost reductions to allow solar hydrogen to directly compete on a levelized cost basis with hydrogen produced from fossil energy. Specifically a cost of CO₂ greater than ∼$800 (ton CO₂)−1 was estimated to be necessary for base-case PEC hydrogen to reach price parity with hydrogen derived from steam reforming of methane priced at $12 GJ⁻¹ ($1.39 (kg H₂)⁻¹). A comparison with low CO₂ and CO₂-neutral energy sources indicated that base-case PEC hydrogen is not currently cost-competitive with electrolysis using electricity supplied by nuclear power or from fossil-fuels in conjunction with carbon capture and storage. Solar electricity production and storage using either batteries or PEC hydrogen technologies are currently an order of magnitude greater in cost than electricity prices with no clear advantage to either battery or hydrogen storage as of yet. Significant advances in PEC technology performance and system cost reductions are necessary to enable cost-effective PEC-derived solar hydrogen for use in scalable grid-storage applications as well as for use as a chemical feedstock precursor to CO₂-neutral high energy-density transportation fuels. Hence such applications are an opportunity for foundational research to contribute to the development of disruptive approaches to solar fuels generation systems that can offer higher performance at much lower cost than is provided by current embodiments of solar fuels generators. Efforts to directly reduce CO₂ photoelectrochemically or electrochemically could potentially produce products with higher value than hydrogen but many as yet unmet challenges include catalytic efficiency and selectivity and CO₂ mass transport rates and feedstock cost. Major breakthroughs are required to obtain viable economic costs for solar hydrogen production but the barriers to achieve cost-competitiveness with existing large-scale thermochemical processes for CO₂ reduction are even greater.

As of 2003 15 hydrogen refuelling stations (HRSs) have been deployed in the Netherlands. To become established the HRS has to go through a permitting procedure. An important document of the permitting dossier is the quantitative risk assessment (QRA) as it assesses the risks of the HRS associated to people and buildings in the vicinity of the HRS. In the Netherlands a generic prescribed approach exists on how to perform a QRA however specific guidelines for HRSs do not exist. An intercomparison among the QRAs of permitted HRSs has revealed significant inconsistencies on various aspects of the QRA: namely the inclusion of HRS sub-systems and components the HRS sub-system and component considerations as predefined components the application of failure scenarios the determination of failure frequencies the application of input parameters the consideration of preventive and mitigation measures as well as information provided regarding the HRS surroundings and the societal risk. It is therefore recommended to develop specific QRA guidelines for HRSs.

One of the options to reduce the dependence on fossil fuels is to produce gas with the quality of natural gas but based on renewable energy sources. It can encompass among other biogas generation from various types of biomass and its subsequent upgrading. The main aim of this study is to analyze under a combined technical economic and environmental perspective three of the most representative technologies for the production of biomethane (bio-based natural gas): (i) manure fermentation and its subsequent upgrading by CO₂ removal (ii) manure fermentation and biogas methanation using renewable hydrogen from electrolysis and (iii) biomass gasification in the atmosphere of oxygen and methanation of the resulted gas. Thermodynamic economic and environmental analyses are conducted to thoroughly compare the three cases. For these purposes detailed models in Aspen Plus software were built while environmental analysis was performed using the Life Cycle Assessment methodology. The results show that the highest efficiency (66.80%) and the lowest break-even price of biomethane (19.2 €/GJ) are reached for the technology involving fermentation and CO₂ capture. Concerning environmental assessment the system with the best environmental performance varies depending on the impact category analyzed being the system with biomass gasification and methanation a suitable trade-off solution for biomethane production.

High hydrogen content fuels can be used in gas turbine for power generation with CO₂ capture IGCC plants or with hydrogen from renewables. The challenge for the engine is the high reactive combustion properties making dilution necessary to mitigate NO_x emissions at the expense of a significant energy cost. In the concept analysed in this study high Exhaust Gas Recirculation (EGR) rate is applied to the gas turbine to generate oxygen depleted air. As a result combustion temperature is inherently limited keeping NO_x emissions low without the need for dilution or unsafe premixing. The concept is analysed by process simulation based on a reference IGCC plant with CO₂ Capture. Results with dry and wet EGR options are presented as a function EGR rate. Efficiency performance is assessed against the reference power cycle with nitrogen dilution. All EGR options are shown to represent an efficiency improvement. Nitrogen dilution is found to have a 1.3% efficiency cost. Although all EGR options investigated offer an improvement dry EGR is considered as the preferred option despite the need for higher EGR rate as compared with the wet EGR. The efficiency gain is calculated to be of 1% compared with the reference case.

In addition to methane gas higher-value resources such as hydrogen gas are produced during anaerobic wastewater treatment. They are however immediately consumed by other organisms. To recover these high-value resources not only do the desired phenotypes need to be retained in the anaerobic reactor but the undesired ones need to be washed out. In this study a well-established alginate-based polymer gel with and without a coating layer was used to selectively encapsulate hydrogen-producing biomass in beads to achieve high-rate recovery of hydrogen during anaerobic wastewater treatment. The effect of cross-linking agents Ca²+ Sr²⁺ and Ba²⁺ as well as a composite coating on the beads consisting of alternating layers of polyethylenimine and silica hydrogel were investigated with respect to their performance specifically their mass transfer characteristics and their differential ability to retain the encapsulated biomass. Although the coating reduced the escape rate of encapsulated biomass from the beads all alginate polymer matrices without coating effectively retained biomass. Fast diffusion of dissolved organic carbon (DOC) through the polymer gel was observed in both Ca-alginate and Sr-alginate without coating. The coating however decreased either the diffusivity or the permeability of the DOC depending on whether the DOC was from synthetic wastewater (more lipids and proteins) or real brewery wastewater (more sugars). Consequently the encapsulation system with coating became diffusion limited when brewery wastewater with high chemical oxygen demand was fed resulting in a lower hydrogen production rate than the uncoated encapsulation systems. In all cases the encapsulated biomass was able to produce hydrogen even at a hydraulic residence time of 45 min. Although there are limitations to this system the used of encapsulated biomass for resource recovery from wastewater shows promise particularly for high-rate systems in which the retention of specific phenotypes is desired.

Aqueous phase reforming of sorbitol was carried out in a 1.7 m long 320 mm ID microchannel reactor with a 5 mm Pt-based washcoated catalyst layer combined with nitrogen stripping. The performance of this microchannel reactor is correlated to the mass transfer properties reaction kinetics hydrogen selectivity and product distribution. Mass transfer does not affect the rate of sorbitol consumption which is limited by the kinetics of the reforming reaction. Mass transfer significantly affects the hydrogen selectivity and the product distribution. The rapid consumption of hydrogen in side reactions at the catalyst surface is prevented by a fast mass transfer of hydrogen from the catalyst site to the gas phase in the microchannel reactor. This results in a decrease of the concentration of hydrogen at the catalyst surface which was found to enhance the desired reforming reaction rate at the expense of the undesired hydrogen consuming reactions. Compared to a fixed bed reactor the selectivity to hydrogen in the microchannel reactor was increased by a factor of 2. The yield of side products (mainly C3 and heavier hydrodeoxygenated species) was suppressed while the yield of hydrogen was increased from 1.4 to 4 moles per mole of sorbitol fed.

Since the beginning of the twenty-first century the limitations of the fossil age with regard to the continuing growth of energy demand the peaking mining rate of oil the growing impact of CO₂ emissions on the environment and the dependency of the economy in the industrialized world on the availability of fossil fuels became very obvious. A major change in the energy economy from fossil energy carriers to renewable energy fluxes is necessary. The main challenge is to efficiently convert renewable energy into electricity and the storage of electricity or the production of a synthetic fuel. Hydrogen is produced from water by electricity through an electrolyser. The storage of hydrogen in its molecular or atomic form is a materials challenge. Some hydrides are known to exhibit a hydrogen density comparable to oil; however these hydrides require a sophisticated storage system. The system energy density is significantly smaller than the energy density of fossil fuels. An interesting alternative to the direct storage of hydrogen are synthetic hydrocarbons produced from hydrogen and CO₂ extracted from the atmosphere. They are CO₂ neutral and stored like fossil fuels. Conventional combustion engines and turbines can be used in order to convert the stored energy into work and heat.

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This session contained talks on the characterization of hydrogen-enhanced corrosion of steels and nickel-based alloys emphasizing the different observations across length scales from atomic-scale spectrographic to macro-scale fractographic examinations.

This article is the transcription of the recorded discussion of the session ‘Hydrogen Effects in Corrosion’ at the Royal Society discussion meeting Challenges of Hydrogen and Metals 16–18 January 2017. The text is approved by the contributors. M.A.S. transcribed the session and E.L.S. assisted in the preparation of the manuscript.

Link to document download on Royal Society Website

This paper presents a study undertaken on a naturally aspirated direct injection diesel engine investigating the combustion and emission characteristics of CH₄-CO₂  and CH₄-CO₂ -H₂ mixtures. These aspirated gas mixtures were pilot-ignited by diesel fuel while the engine load was varied between 0 and 7 bar IMEP by only adjusting the flow rate of the aspirated mixtures. The in-cylinder gas composition was also investigated when combusting CH₄-CO₂ and CH₄-CO₂-H₂ mixtures at different engine loads with in cylinder samples collected using two different sampling arrangements. The results showed a longer ignition delay period and lower peak heat release rates when the proportion of CO₂ was increased in the aspirated mixture. Exhaust CO₂ emissions were observed to be higher for 60 CH₄:40CO₂ mixture but lower for the 80CH₄:20CO₂ mixture as compared to diesel fuel only combustion at all engine loads. Both exhaust and in-cylinder NO_x levels were observed to decrease when the proportion of CO₂ was increased; NO_x levels increased when the proportion of H₂ was increased in the aspirated mixture. In-cylinder NO_x levels were observed to be higher in the region between the sprays as compared to within the spray core attributable to higher gas temperatures reached post ignition in that region.

The present review provides a catalogue of relevant renewable energy (RE) technologies currently available (regarding the 2030 scope) and to be available in the transition towards 2050 for the decarbonisation of Energy Intensive Industries (EIIs). RE solutions have been classified into technologies based on the use of renewable electricity and those used to produce heat for multiple industrial processes. Electrification will be key thanks to the gradual decrease in renewable power prices and the conversion of natural-gas-dependent processes. Industrial processes that are not eligible for electrification will still need a form of renewable heat. Among them the following have been identified: concentrating solar power heat pumps and geothermal energy. These can supply a broad range of needed temperatures. Biomass will be a key element not only in the decarbonisation of conventional combustion systems but also as a biofuel feedstock. Biomethane and green hydrogen are considered essential. Biomethane can allow a straightforward transition from fossil-based natural gas to renewable gas. Green hydrogen production technologies will be required to increase their maturity and availability in Europe (EU). EIIs’ decarbonisation will occur through the progressive use of an energy mix that allows EU industrial sectors to remain competitive on a global scale. Each industrial sector will require specific renewable energy solutions especially the top greenhouse gas-emitting industries. This analysis has also been conceived as a starting point for discussions with potential decision makers to facilitate a more rapid transition of EIIs to full decarbonisation.

Chemical looping combustion (CLC) is a promising method for power production with integrated CO₂ capture with almost no direct energy penalty. When integrated into a natural gas combined cycle (NGCC) plant however CLC imposes a large indirect energy penalty because the maximum achievable reactor temperature is far below the firing temperature of state-of-the-art gas turbines. This study presents a techno-economic assessment of a CLC plant that circumvents this limitation via an added combustor after the CLC reactors. Without the added combustor the energy penalty amounts to 11.4%-points causing a high CO₂ avoidance cost of $117.3/ton which is more expensive than a conventional NGCC plant with post-combustion capture ($93.8/ton) with an energy penalty of 8.1%-points. This conventional CLC plant would also require a custom gas turbine. With an added combustor fired by natural gas a standard gas turbine can be deployed and CO2 avoidance costs are reduced to $60.3/ton mainly due to a reduction in the energy penalty to only 1.4%-points. However due to the added natural gas combustion after the CLC reactor CO₂ avoidance is only 52.4%. Achieving high CO₂ avoidance requires firing with clean hydrogen instead increasing the CO₂ avoidance cost to $96.3/ton when a hydrogen cost of $15.5/GJ is assumed. Advanced heat integration could reduce the CO₂ avoidance cost to $90.3/ton by lowering the energy penalty to only 0.6%-points. An attractive alternative is therefore to construct the plant for added firing with natural gas and retrofit the added combustor for hydrogen firing when CO₂ prices reach very high levels.

This paper describes a combined experimental analytical and numerical modelling investigation into hydrogen jet fires in a passively ventilated enclosure. The work was funded by the EU Fuel Cells and Hydrogen Joint Undertaking project Hyindoor. It is relevant to situations where hydrogen is stored or used indoors. In such situations passive ventilation can be used to prevent the formation of a flammable atmosphere following a release of hydrogen. Whilst a significant amount of work has been reported on unignited releases in passively ventilated enclosures and on outdoor hydrogen jet fires very little is known about the behaviour of hydrogen jet fires in passively ventilated enclosures. This paper considers the effects of passive ventilation openings on the behaviour of hydrogen jet fires. A series of hydrogen jet fire experiments were carried out using a 31 m3 passively ventilated enclosure. The test programme included subsonic and chocked flow releases with varying hydrogen release rates and vent configurations. In most of the tests the hydrogen release rate was sufficiently low and the vent area sufficiently large to lead to a well-ventilated jet fire. In a limited number of tests the vent area was reduced allowing under-ventilated conditions to be investigated. The behaviour of a jet fire in a passively ventilated enclosure depends on the hydrogen release rate the vent area and the thermal properties of the enclosure. An analytical model was used to quantify the relative importance of the hydrogen release rate and vent area whilst the influence of the thermal properties of the enclosure were investigated using a CFD model. Overall the results indicate that passive ventilation openings that are sufficiently large to safely ventilate an unignited release will tend to be large enough to prevent a jet fire from becoming under-ventilated.

Hydrogen generated during core meltdown accidents in nuclear reactors can cause serious threat to the structural integrity of the containment and safe operation of nuclear power plants. The study of hydrogen release and mixing within the containments is an important area of safety research as hydrogen released during such accidents in nuclear power plants can lead to hydrogen explosions and catastrophic consequences. A small scale experimental setup called the AERB-IIT Madras Hydrogen Mixing Studies (AIHMS) facility is setup at IIT Madras to study the distribution of hydrogen subsequent to release as a jet followed by its response to various wall thermal conditions. The present paper gives details of the design fabrication and instrumentation of the AIHMS facility and a comparison of features of the facility with respect to other facilities existing for hydrogen mitigation studies. Then it gives details of the experiments conducted and the results of the preliminary experiments on concentration build-up as a result of injection of gases (air and helium) and effect of thermally induced natural convection on gas mixing performed in this experimental facility.

The present work proposes a parametric study on the influence of the height of the release source on the helium dispersion regimes inside a naturally ventilated enclosure. Several configurations were experimentally addressed in order to improve knowledge on dispersion considering conditions close to hydrogen energy systems in terms of operating characteristics and design. Thus the varying parameters of the study were mainly the height of the release and also the releasing flow rate the volume and the geometry of the enclosure. Experimental results were compared to existing analytical models and considered through model improvements allowing a better approach of these specific cases for hydrogen systems risk assessment.

Gasification of excavated landfill waste is one of the promising options to improve the added-value chain during remediation of problematic old landfill sites. Steam gasification is considered as a favorable route to convert landfill waste into H₂-rich syngas. Co-gasification of such a poor quality landfill waste with biochar or biomass would be beneficial to enhance the H₂ concentration in the syngas as well as to improve the gasification performance. In this work steam co-gasification of landfill waste with biochar or biomass was carried out in a lab-scale reactor. The effect of the fuel blending ratio was investigated by varying the auxiliary fuel content in the range of 15e35 wt%. Moreover co-gasification tests were carried out at temperatures between 800 and 1000°C. The results indicate that adding either biomass or biochar enhances the H₂ yield where the latter accounts for the syngas with the highest H₂ concentration. At 800°C the addition of 35 wt% biochar can enhance the H₂ concentration from 38 to 54 vol% and lowering the tar yield from 0.050 to 0.014 g/g-fuel-daf. No apparent synergetic effect was observed in the case of biomass co-gasification which might cause by the high Si content of landfill waste. In contrast the H₂ production increases non-linearly with the biochar share in the fuel which indicates that a significant synergetic effect occurs during co-gasification due to the reforming of tar over biochar. Increasing the temperature of biochar co-gasification from 800 to 1000°C elevates the H₂ concentration but decreases the H₂/CO ratio and increases the tar yield. Furthermore the addition of biochar also enhances the gasification efficiency as indicated by increased values of the energy yield ratio.

In order to reduce anthropogenic global warming governments around the world have decided to reduce CO₂ emissions from fossil fuels dramatically within the next decades. In moderate and cold climates large amounts of fossil fuels are used for space heating and domestic hot water production in winter. Although on an annual base solar energy is available in large quantities in these regions least of the solar resource is available in winter when most of the energy is needed. Therefore solutions are needed to store and transfer renewable energy from summer to winter. In this paper a seasonal energy storage based on the aluminium redox cycle (Al3+→Al→ Al3+) is proposed. For charging electricity from solar or other renewable sources is used to convert aluminium oxide or aluminium hydroxide to elementary aluminium (Al3+→Al). In the discharging process aluminium is oxidized (Al→Al3+) releasing hydrogen heat and aluminium hydroxide or aluminium oxide as a by-product. Hydrogen is used in a fuel cell to produce electricity. Heat produced from the aluminium oxidation process and by the fuel cell is used for domestic hot water production and space heating. The chemical reactions and energy balances are presented and simulation results are shown for a system that covers the entire energy demand for electricity space heating and domestic hot water of a new multi-family building with rooftop photovoltaic energy in combination with the seasonal Al energy storage cycle. It shows that 7–11 kWp of photovoltaic installations and 350–530 kg Al would be needed per apartment for different Swiss climates. Environmental life cycle data shows that the global warming potential and non-renewable primary energy consumption can be reduced significantly compared to today's common practice of heating with natural gas and using electricity from the ENTSO-E network. The presumptive cost were estimated and indicate a possible cost-competitiveness for this system in the near future.

Minimising tailpipe emissions and the decarbonisation of transport in a cost effective way remains a major objective for policymakers and vehicle manufacturers. Current trends are rapidly evolving but appear to be moving towards solutions in which vehicles which are increasingly electrified. As a result we will see a greater linkage between the wider energy system and the transportation sector resulting in a more complex and mutual dependency. At the same time major investments into technological innovation across both sectors are yielding rapid advancements into on-board energy storage and more compact/lightweight on-board electricity generators. In the absence of sufficient technical data on such technology holistic evaluations of the future transportation sector and its energy sources have not considered the impact of a new generation of innovation in propulsion technologies. In this paper the potential impact of a number of novel powertrain technologies are evaluated and presented. The analysis considers heavy duty vehicles with conventional reciprocating engines powered by diesel and hydrogen hybrid and battery electric vehicles and vehicles powered by hydrogen fuel cells and freepiston engine generators (FPEGs). The benefits are compared for each technology to meet the expectations of representative medium and heavy-duty vehicle drivers. Analysis is presented in terms of vehicle type vehicle duty cycle fuel economy greenhouse gas (GHG) emissions impact on the vehicle etc.. The work shows that the underpinning energy vector and its primary energy source are the most significant factor for reducing primary energy consumption and net CO₂ emissions. Indeed while an HGV with a BEV powertrain offers no direct tailpipe emissions it produces significantly worse lifecycle CO2 emissions than a conventional diesel powertrain. Even with a de-carbonised electricity system (100 g CO2/kWh) CO₂ emissions are similar to a conventional Diesel fuelled HGV. For the HGV sector range is key to operator acceptability of new powertrain technologies. This analysis has shown that cumulative benefits of improved electrical powertrains on-board storage efficiency improvements and vehicle design in 2025 and 2035 mean that hydrogen and electric fuelled vehicles can be competitive on gravimetric and volumetric density. Overall the work demonstrates that presently there is no common powertrain solution appropriate for all vehicle types but how subtle improvements at a vehicle component level can have significant impact on the design choices for the wider energy system.

Developing low-cost high-performance catalysts is of fundamental significance for electrochemical energy conversion and storage. In recent years metal@carbon core@shell nanocomposites have emerged as a unique class of functional nanomaterials that show apparent electrocatalytic activity towards a range of reactions such as hydrogen evolution reaction oxygen evolution reaction oxygen reduction reaction and CO2 reduction reaction that are important in water splitting fuel cells and metal-air batteries. The activity is primarily attributed to interfacial charge transfer from the metal core to the carbon shell that manipulate the electronic interactions between the catalyst surface and reaction intermediates and varies with the structures and morphologies of the metal core (elemental composition core size etc.) and carbon shell (doping layer thickness etc.). Further manipulation can be achieved by the incorporation of a third structural component. A perspective is also included highlighting the current gap between theoretical modeling and experimental results and technical challenges for future research.

The co-combustion of diesel fuel with H2 presents a promising route to reduce the adverse effects of diesel engine exhaust pollutants on the environment and human health. This paper presents the results of H2-diesel co-combustion experiments carried out on two different research facilities a light duty and a heavy duty diesel engine. For both engines H2 was supplied to the engine intake manifold and aspirated with the intake air. H2 concentrations of up to 20% vol/vol and 8% vol/vol were tested in the light duty and heavy duty engines respectively. Exhaust gas circulation (EGR) was also utilised for some of the tests to control exhaust NOx emissions.<br/>The results showed NOx emissions increase with increasing H2 in the case of the light duty engine however in contrast for the heavy duty engine NOx emissions were stable/reduced slightly with H2 attributable to lower in-cylinder gas temperatures during diffusion-controlled combustion. CO and particulate emissions were observed to reduce as the intake H2 was increased. For the light duty H2 was observed to auto-ignite intermittently before diesel fuel injection had started when the intake H2 concentration was 20% vol/vol. A similar effect was observed in the heavy duty engine at just over 8% H2 concentration.

The different CFD tools used by the NoE HySafe partners are applied to a series of integral complex Standard Benchmark Exercise Problems (SBEPs). All benchmarks cover complementarily physical phenomena addressing application relevant scenarios and refer to associated experiments with an explicit usage of hydrogen. After the blind benchmark SBEPV1 and SBEPV3 with subsonic vertical release in a large vessel and in a garage like facility SBEPV4 with a horizontal under-expanded jet release through a small nozzle SBEPV5 covers the scenario of a subsonic horizontal jet release in a multi-compartment room.<br/>As the associated dispersion experiments conducted by GEXCON Norsk Hydro and STATOIL were disclosed to the participants the whole benchmark was conducted openly. For the purpose of validation only the low momentum test D27 had to be simulated.<br/>The experimental rig consists of a 1.20 m x 0.20 m x 0.90 m (Z vertical) vessel divided into 12 compartments partially even physically by four baffle plates. In each compartment a hydrogen concentration sensor is mounted. There is one vent opening at the wall opposite the release location centrally located about 1 cm above floor with dimensions 0.10 m (Y) times 0.20 m (Z). The first upper baffle plate close to the release point is on a sensitive location as it lies nearly perfectly in the centre of the buoyant jet and thus separates the flow into the two compartments. The actual release was a nominally constant flow of 1.15 norm liters for 60 seconds. With a 12mm nozzle diameter this corresponds to an average exit velocity of 10.17 m/s.<br/>6 CFD packages have been applied by 7 HySafe partners to simulate this experiment: ADREAHF by NCSRD FLACS by GexCon and DNV KFX by DNV FLUENT by UPM and UU CFX by HSE/HSL and GASFLOW by FZK. The results of the different participants are compared against the experimental data. Sensitivity studies were conducted by FZK using GASFLOW and by DNV applying KFX.<br/>Conclusions based on the comparisons and the sensitivity studies related to the performance of the applied turbulence models and discretisation schemes in the release and diffusion phase are proposed. These are compared to the findings of the previous benchmark exercises.

An experimental study of flame propagation acceleration and transition to detonation in hydrogen-air mixture in 2 m long rectangular cross section channel filled with obstacles located at the bottom wall was performed. The initial conditions of the hydrogen-air mixture were 0.1 MPa and 293 K. Three different cases of obstacle height (blockage ratio 0.25 0.5 and 0.75) and four cases of obstacle density were studied with the channel height equal to 0.08 m. The channel width was 0.11 m in all experiments. The propagation of flame and pressure waves was monitored by four pressure transducers and four in house ion probes. The pairs of transducers and probes were placed at various locations along the channel in order to get information about the progress of the phenomena along the channel. To examine the influence of mixture composition on flame propagation and DDT the experiments were performed for the compositions of 20% 25% and 29.6% of H2 in air by volume. As a result of the experiments the deflagration and detonation regimes and velocities of flame propagation in the obstructed channel were determined.

This study deals with the TNO Multi-Energy and Baker-Strehlow-Tang (BST) methods for estimating the positive overpressures and positive impulses resulting from hydrogen-air explosions. With these two methods positive overpressure and positive impulse results depend greatly on the choice of the class number for the TNO Multi-Energy method or the Mach number for the BST methods. These two factors permit the user to read the reduced parameters of the blast wave from the appropriate monographs for each of these methods i.e. positive overpressure and positive duration phase for the TNO Multi-Energy method and positive overpressure and positive impulse for the BST methods. However for the TNO Multi-Energy method the determination of the class number is not objective because it is the user who makes the final decision in choosing the class number whereas with the BST methods the user is strongly guided in their choice of an appropriate Mach number. These differences in the choice of these factors can lead to very different results in terms of positive overpressure and positive impulse. Therefore the objective of this work was to compare the positive overpressures and positive impulses predicted with the TNO Multi-Energy and BST methods with data available from large-scale experiments.

In this work first-principles methods were performed to simulate interactions between hydrogen and common alloying elements of high strength low alloy (HSLA) steel. The world has been convinced that hydrogen could be one of the future clean energy sources. HSLA steel with a balance of strength toughness and hydrogen embrittlement susceptibility is expected for application in large-scale hydrogen storage and transportation. To evaluate the property deterioration under a hydrogen atmosphere hydrogen embrittlement (HE) of HSLA steel attracts attention. However due to the small size of hydrogen atoms the mechanism of HE is challenging to observe directly by current experimental methods. To understand the HE mechanism at an atomic level DFT methods were applied to simulate the effects of alloying elements doping in bcc-Fe bulk structure and grain boundary structure. Furthermore the potential application of DFT to provide theoretical advice for HSLA steel design is discussed.